linux-kernel - Re: [PATCH v2 1/2] of: reserved_mem: Try to keep range allocations contiguous

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Date:   Tue, 20 Jun 2023 09:34:53 -0600
From:   Rob Herring <robh@...nel.org>
To:     Stephan Gerhold <stephan@...hold.net>
Cc:     devicetree@...r.kernel.org,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        devicetree-spec@...r.kernel.org,
        Conor Dooley <conor+dt@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Rob Herring <robh+dt@...nel.org>, linux-kernel@...r.kernel.org,
        Frank Rowand <frowand.list@...il.com>,
        linux-arm-msm@...r.kernel.org, Andy Gross <agross@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>
Subject: Re: [PATCH v2 1/2] of: reserved_mem: Try to keep range allocations
 contiguous


On Wed, 14 Jun 2023 21:20:42 +0200, Stephan Gerhold wrote:
> Right now dynamic reserved memory regions are allocated either
> bottom-up or top-down, depending on the memblock setting of the
> architecture. This is fine when the address is arbitrary. However,
> when using "alloc-ranges" the regions are often placed somewhere
> in the middle of (free) RAM, even if the range starts or ends next
> to another (static) reservation.
> 
> Try to detect this situation, and choose explicitly between bottom-up
> or top-down to allocate the memory close to the other reservations:
> 
>   1. If the "alloc-range" starts at the end or inside an existing
>      reservation, use bottom-up.
>   2. If the "alloc-range" ends at the start or inside an existing
>      reservation, use top-down.
>   3. If both or none is the case, keep the current
>      (architecture-specific) behavior.
> 
> There are plenty of edge cases where only a more complex algorithm
> would help, but even this simple approach helps in many cases to keep
> the reserved memory (and therefore also the free memory) contiguous.
> 
> Signed-off-by: Stephan Gerhold <stephan@...hold.net>
> ---
>  drivers/of/of_reserved_mem.c | 55 ++++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 53 insertions(+), 2 deletions(-)
> 

Applied, thanks!